Integrated circuit comprising on-chip resistors with plurality of first and second terminals coupled to the resistor body

ABSTRACT

An integrated circuit (IC) is disclosed. The IC includes a substrate with a resistor region and a resistor body disposed on the resistor region. A plurality of first resistor contact strips and a plurality of second resistor contact strips are disposed on the resistor body along a first direction. Two adjacent first and second resistor contact strips are separated by a respective one of contact strip spaces. The IC includes a plurality of first terminals and a plurality of second terminals. Each of the first terminals is coupled to a respective one of the first resistor contact strips while each of the second terminals is coupled to a respective one of the second resistor contact strips. A set of the first terminal and the second terminal forms first and second terminals of an on-chip resistor.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of U.S. ProvisionalApplication Ser. No. 61/655,999, filed on Jun. 5, 2012, which is hereinincorporated by reference in its entirety.

BACKGROUND

Current sensing resistors are widely used in integrated circuits (ICs)to monitor the current in the circuit and translate the amount ofcurrent into a voltage that can be easily measured and monitored. Suchresistors need to have low resistance value (in the range of 10 mΩ to200 mΩ), low temperature coefficient of resistance (TCR, typicallyaround 50 ppm/° C.), high current range (100 mA to 5 A, and typicallyaround 1 A) and good heat dissipation. Current sensing resistors areimplemented off the IC (e.g., off-chip). To accommodate the off-chipresistors, additional area is needed in the package or circuit board,increasing the overall foot print of the IC. Furthermore, off-chipresistors have corresponding manufacturing cost. Accordingly, the issuesassociated with off-chip resistors increase overall manufacturing costsas well as design flexibility.

It is describable to provide device structures and methods that allowintegration of off-chip current sensing resistors as part of the chip ina cost effective way.

SUMMARY

Embodiments generally relates to semiconductor devices. In oneembodiment, an integrated circuit (IC) is disclosed. The IC includes asubstrate with a resistor region and a resistor body disposed on theresistor region. A plurality of first resistor contact strips and aplurality of second resistor contact strips are disposed on the resistorbody along a first direction. Two adjacent first and second resistorcontact strips are separated by a respective one of contact stripspaces. The IC includes a plurality of first terminals and a pluralityof second terminals. Each of the first terminals is coupled to arespective one of the first resistor contact strips while each of thesecond terminals is coupled to a respective one of the second resistorcontact strips. A set of the first terminal and the second terminalforms first and second terminals of an on-chip resistor.

In another embodiment, an integrated circuit (IC) is presented. The ICincludes a substrate with a resistor region and a resistor body disposedon the resistor region. The IC includes a plurality of first terminalsand a plurality of second terminals coupled to the resistor body. A setof the first terminal and the second terminal forms first and secondterminals of an on-chip resistor.

These embodiments, along with other advantages and features hereindisclosed, will become apparent through reference to the followingdescription and the accompanying drawings. Furthermore, it is to beunderstood that the features of the various embodiments described hereinare not mutually exclusive and can exist in various combinations andpermutations.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the present disclosure. In the followingdescription, various embodiments of the present disclosure are describedwith reference to the following drawings, in which:

FIG. 1A is a top view of a resistor portion of a device in accordancewith an embodiment of the present disclosure.

FIG. 1B is a cross-sectional view of the resistor portion of FIG. 1Aalong line A-A′ in accordance with an embodiment of the presentdisclosure.

FIG. 2 is a cross-sectional view of a resistor portion of a device inaccordance with another embodiment of the present disclosure.

FIG. 3 is a top view of an integrated circuit layout including bond padstructures in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure provides a cost effective solution to integrate acurrent sensing resistor in an integrated-circuit chip.

FIG. 1A illustrates a top view of a resistor portion of an embodiment ofa device 100. FIG. 1B illustrates a cross-sectional view of the resistorportion of the device of FIG. 1A along line A-A′. The device, forexample, is an integrated circuit (IC). The IC may be any type of IC.Other types of devices may also be useful. The IC may be incorporatedinto various types of consumer electronic products or other products.

Referring to FIGS. 1A and 1B, the device includes a substrate 110. Thesubstrate may be a semiconductor substrate. For example, the substratemay be a silicon substrate. Other types of substrates, such as asilicon-on-insulator (SOI) substrate, may also be useful. The substrateincludes a resistor region. For example, the resistor region serves as aregion on which an on-chip resistor is disposed. The on-chip resistor,in one embodiment, is a thin film resistor. Although the portion of thedevice only shows a resistor region, it is understood that the devicemay include additional resistor regions. Furthermore, other regions mayalso be included. For example, the device may include a logic region.The logic region may include high voltage, medium voltage and/or lowvoltage regions. Other types of regions may also be included. Forexample, the device may include a memory region.

The resistor region includes an isolation region 115. The isolationregion, for example, may be a trench isolation region, such as a shallowtrench isolation (STI) region. Other types of isolation regions may alsobe useful. The trench isolation region may be formed by etching a trench(or recess) in a surface of the substrate and filling the trench with adielectric material. Excess dielectric material may be removed by, forexample, polishing, such as chemical mechanical polishing (CMP). Thedielectric material of the trench isolation region may include silicondioxide, silicon nitride, silicon oxy-nitride, and fluoride-dopedsilicate. Other types of dielectric materials may also be useful. Theisolation region defines the resistor region.

A resistor body 120 is disposed in the resistor region. For example, theresistor body is disposed on and within the boundaries of the isolationregion. The resistor body is formed of a thin film resistor material.Preferably, the resistor body is a thin film resistor material having agood TCR performance. For example, the resistor body has minimalresistance variation with changing temperature. The TCR value may bepositive or negative depending on the type of resistor material used. Aresistor with a positive TCR exhibits an increase in resistance withincreasing temperature, while a resistor with a negative TCR exhibits adecrease in resistance with increasing temperature. The resistor bodymay be, for example, polysilicon, Ta, or TaN. In one embodiment, theresistor body is formed of heavily doped polysilicon. In one embodiment,the resistor body is formed of heavily doped p-type polysilicon (P⁺Poly). Providing a heavily n-doped polysilicon (N⁺ Poly) resistor bodymay also be useful. Other types of resistor materials may also be usedfor the resistor body. As shown, the resistor body is rectangular inshape. Providing a resistor body with other geometric shapes may also beuseful.

A plurality of resistor contact strip regions 140 are defined on thesurface of the resistor body. The contact strip regions, for example,are disposed in parallel along a first direction. The contact stripregions are separated by space regions 130, creating distant contactstrip regions. For example, the resistor body includes Y contact stripregions with Y-1 space regions, where Y is an integer greater than 1. Inother embodiments, the number of contact strip is equal to 2^(Y), whereY is an integer number ≧ to 2. Other configurations of the resistor bodymay also be useful. Illustratively, the resistor body includes 4contactstrip regions and 3 space regions. The contact strip region includesresistor contact strips. The resistor contact strips may be made by thesame material as that of the resistor body.

In one embodiment, the contact strip regions 140 include metal silicidecontact strips. Metal silicide contact strips, for example, are providedfor a silicon type resistor body, such as P⁺ Poly. Providing metalsilicide contact strips reduces contact resistance of polysilicon.Various types of metal silicides may be used. For example, nickelsilicide, titanium silicide, cobalt silicide, tungsten silicide orplatinum silicide may be used. As for the space regions 130, theyinclude silicide blocks. Silicide blocks, for example, are dielectricblocks which prevent formation of metal silicide on the resistor block.Various types of dielectric materials, such as silicon oxide, siliconoxynitride, or silicon nitride, may be used.

In other embodiment, such as for metal-based resistor bodies, metalsilicide contact strips may not be needed, as shown in FIG. 2. In suchcases, the contact strips may be part of the resistor body. Furthermore,metal silicide blocks may not be needed since no silicide contact stripsare used.

The metal silicide resistor contact strips may be formed by aself-aligned silicide (silicide) process. Other techniques for formingthe resistor contact strips may also be useful. The process includes,for example, first forming silicide blocks in the space regions on theresistor body. For example blanket silicide block layer is formed on thesubstrate, covering the resistor body. Using a patterned mask layer,such as photoresist, the blanket layer is etched to form the silicideblocks. The etch, for example, may be an anisotropic etch, such as areactive ion etch (RIE). As shown the silicide block extends beyond theresistor body to ensure that resistor body in the space regions is notexposed. A metal layer, such as nickel, titanium, tungsten, cobalt orplatinum or alloys thereof, is disposed on the substrate, covering theresistor body and silicide block. The subsequent annealing causes areaction between the metal and expose portions of the polysiliconresistor body to form metal silicide. No silicide is formed in the spaceregions of the resistor body due to the silicide blocks. Unreacted metalis removed by, for example, a wet etch, leaving metal silicide strips onthe resistor body.

The resistor contact strips 140 are configured into first and secondcontact strips 140 _(a) and 140 _(b). A portion 126 of the resistor bodybetween the resistors strips forms a resistor. For example, the portionof the resistor body below the silicide block forms a resistor. Thefirst contact strip 140 _(a) may serve as a first terminal of theresistor while the second contact strip 140 _(b) may serve as a secondterminal of the resistor. In the case where Y is an even number andgreater than 2, such as 4or greater, the resistor contact strips areconfigured into Y/2 sets of alternating first and second resistorcontact strips 140 _(a) and 140 _(b). Portions between the resistorstrips form Y-1 resistors. The final resistance of the resistor will bedetermined by the number of resistors formed which is in turn determinedby the dimension (i.e., length and width) of the resistor body.

A dielectric layer is disposed on the substrate. The dielectric layercovers the substrate 110 and resistor body 120, including the resistorcontact strips 140 and contact spaces 130. As shown, the dielectriclayer covers the substrate and resistor body, including the silicidecontact strips and silicide blocks. A dielectric layer serves as aninterlevel dielectric (ILD) layer. The ILD layer includes a contact orvia level 182 and an interconnect or metal level 186. Contacts 150 aredisposed in the contact level 182 and metal lines 160 are disposed inthe metal level 186. As discussed, an IC may include numerous metallevels. For example, an IC may include X metal levels, where X is thetop metal level and 1 is the lowest metal level. For example, an IC mayhave metal levels M₁to M_(X). A dielectric or ILD layer corresponds to ametal layer.

The dielectric layer disposed over the substrate and resistor body, forexample, is the first ILD layer 180 i. The first dielectric layer mayalso be disposed over other regions of the substrate. For example, thefirst dielectric layer may be disposed over transistors over otherdevice regions of the substrate. The contact level of the first ILDlayer may be referred to as the CA level while the metal level of thefirst ILD layer may be referred to as M₁. Conductive lines 160 ₁ aredisposed in the M₁. As shown, conductive lines are disposed in M₁ alongthe first direction over the resistor contact strips. In one embodiment,the conductive lines of M₁ are configured into sets of first and secondconductive lines 160 _(1a) and 160 _(1b). The first conductive lines 160_(1a) are disposed over first resistor contact strips 140 _(a) andsecond conductive lines 160 _(1b) are disposed over second resistorcontact strips 140 _(b). First conductive contacts 150 _(1a) in CAcouples first conductive lines 160 _(1a) in M₁ to first resistor contactstrips 140 _(a); second conductive contacts 150 _(1b) in CA couplessecond conductive lines 160 _(1b) in M₁ to second resistor contactstrips 140 _(b). Illustratively, a line is provided with 7 contactswhich stitches or couples it to a respective resistor contact strip.Providing other number of contacts for a conductive line may also beuseful. Preferably, a maximum number of contacts may be formed to reducethe contact resistance and to equally distribute the current flow acrossthe resistor.

A terminal ILD layer 180 _(T) is provided in which first and second mainresistor terminals 160 _(Ta) and 160 _(Tb) are disposed. The mainresistor terminals, as shown, are terminal plates. The terminal platestraverse the resistor body along a second direction. The seconddirection is, for example, orthogonal to the first direction. The seconddirection is, for example, parallel to A-A′. Adjacent sides of theterminal plates are separated by a space. The outer perimeter of theterminal plates together has a size and shape similar to the resistorbody. For example, the terminal plates together have a size and shapewhich is about the same as the resistor body, although it can beslightly larger or smaller depending on the space allocated to theresistor on the device. Other configurations of terminal plates may alsobe useful.

The surface areas of the first and second terminal plates are equal. Forexample, the first terminal plate 160 _(Ta) encompasses a first portionof the resistor body along the first direction and the second terminalplate 160 _(Tb) encompasses a second portion of the resistor body alongthe first direction. The size of the first portion is the same as thatof the second portion. The first main resistor terminal 160 _(Ta) iscommonly coupled to first conductive lines 160 _(1a) of the M1 and thesecond main resistor terminal 160 _(Tb) is commonly coupled to secondconductive lines 160 _(1b) of M1. This results in the resistors of theresistor body being coupled in parallel. For example, in the case of 4contact strips which form three resistors, the three resistors arecoupled in parallel.

Since the first terminal 160 _(Ta) and second terminal 160 _(Tb) of aresistor occupies opposite portions of the resistor body, current flowis slanted. In one embodiment, the adjacent sides of the terminal platesare slanted to compensate for the slanted current flow from one terminalof a resistor to the other. For example, the adjacent sides of theterminal plates are slanted at an angle following the direction ofcurrent flow of the resistor, forming trapezoidal shaped terminalplates. As shown, the wider end of the terminal plate is at the highcurrent location and the opposite narrower end is at the lower currentlocation. This reduces the sharpness of the angle of current flow.Providing slanted terminal plates improves current conduction capacity.

The use of slanted terminal plates results in different first metallines having different amount of contacts and different second metallines having different amount of contacts. For example, as shown, afirst terminal of R1 has 4 contacts and the second terminal of R1 has 2contacts while the first terminal of R2 has 2 contacts and the secondterminal of R2 has 4 contacts.

In one embodiment, the terminal ILD layer is the top metal layer. Forexample, the terminal ILD layer is M_(X). For intermediate ILD layers,such as for M₂ through M_(X-1), the pattern may be the metal and viacontact pattern which may be the same as M_(X)until contact is made toconductive lines of M₁. Providing intermediate ILD levels with metalterminal plates in multiple metal levels increases heat dissipationgenerated by current flow. The main terminals are coupled to bond padsof the IC, enabling external access. For example, a first main terminalis coupled to a first bond pad and a second main terminal is coupled toa second bond pad.

As described, M₁ is provided for conductive lines coupled to the contactstrips or directly to the conductive metal resistor body whileM_(X)serves as the terminal ILD layer. It is understood that otherconfigurations of metal layers for various components of the resistormay also be useful. For example, conductive lines may be provided at M₁and coupled directly or indirectly to the contact strips. Likewise, theterminal ILD layer may be any ILD layer above the metal levels of themetal lines. For terminal ILD layer below M_(X), the main terminals maybe coupled to bond pads directly or indirectly to the bond pads.

The size of the resistor body may depend on the technology node (e.g.,45 nm) as well as the material used and desired resistance. For example,technology node determines the CD of the resistor strips and spaceswhile different materials have different sheet resistances, anddepending on the desired resistance, different number of resistorscoupled in parallel may be required. As for the height of the resistorbody, it may be similar to, for example, gates of transistors used inthe logic area. Other configurations of resistor body may also beuseful. As described, the resistor is compatible with current logicprocesses. This provides for easy integration of the resistor into thedevice or IC.

FIG. 2 illustrates a cross-sectional view of a resistor portion of adevice 200 in accordance with another embodiment of the presentdisclosure. The same numeral references are used for those componentssimilar or identical to those in the first embodiment illustrated inFIGS. 1A-1B, and the details described thereof is not repeated herein inthe interest of brevity. In the present embodiment, when an electricallyconductive material, such as metal like Ta and TaN for example, is usedas the resistor body 220, no resistor contact strip regions 140 andspace regions 130 as shown in FIG. 1B are needed. In this case, thecontacts may be directly formed on the resistor body 220. As shown inFIG. 2, a resistor portion 226 of the resistor body 220 between thefirst conductive contacts 150 _(1a) and the second conductive contacts150 _(1b) in contact level 182 forms a resistor.

The resistor of the present disclosure, as described, may be laid out ina multi-finger arrangement on one or several big plates connected inparallel so as to provide minimum process variation impact to thecritical dimension (CD) of resistor body and the resistance value. Withthe multiple resistors of the multi-finger arrangement connected inparallel with respect to each other, a targeted resistor value can beachieved. Moreover, by connecting multiple thin film resistors inparallel, very small values of resistance can be achieved.

The resistor of the present disclosure may be simply integrated into theIC since the integration is compatible with current fabrication process.For example, the resistor body may be formed along with gates oftransistors. In addition, various metal layers are made by the samematerials as those of logic portion.

FIG. 3 illustrates a top view of a layout of an integrated circuit 300including bond pad structures 310 in accordance with an embodiment ofthe present disclosure.

The device 100 or 200 of the present disclosure may be integrated in anintegrated circuit board 300 by a typical IC fabrication process. In oneembodiment, the device 100 or 200 is disposed below bond pads 310 toreduce the integration area and cost. No additional chip area is neededto implement the on-chip resistor. Given that the device 100 or 200,which includes one or more current sensing resistor(s) as describedabove, is a part of an integrated circuit, the current of which issensed by the current sensing resistor(s) in the device 100 or 200. Assuch, techniques of the present disclosure can be used to integrate anyoff-chip resistor into a chip in a cost effective way.

The device 100, having unsalicided P⁺-Poly resistor, demonstrates verygood TCR performance. Data listed in Table 1 below are taken from a 0.13μm integrated-circuit fabrication process. The TCR performance of thedevice 100 of the present disclosure can meet TCR requirement forpractical applications. An example of the device 100 of the presentdisclosure has an effective width ranging from 3,000 μm to 30,000 μm.Taking a typical poly current density of 1 mA/μm, the device 100 of thepresent disclosure can take up current ranging from 3 A to 30 A.

TABLE 1 Characteristics of Current Sensing Resistors Key Resistors[Ω/Sq] TCR1 [ppm/° C.] P+ active resistor 130 1500 P⁺ Poly Resistor 315−50 N⁺ Poly Resistor 300 −1,100 1K HRES Poly 1,000 −1,000 Resistor 2KHRES Poly 2,000 −1,050 Resistor

To further improve TCR performance, a TCR compensation resistor may beprovided. The TCR compensation resistor, in one embodiment, is coupledin parallel with the main resistor. The TCR compensation resistor has anopposite TCR as the main resistor. For example, if the main resistor hasa positive TCR, the compensation resistor has a negative TCR. Forexample, if the main resistor is P⁺-Poly, then the compensation resistoris N⁺-Poly. In one embodiment, the compensation resistor has a smallresistance. The compensation resistor effectively compensates for TCRwhile minimally impacting the overall resistance of the main resistor.

The present disclosure may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Theforegoing embodiments, therefore, are to be considered in all respectsillustrative rather than limiting the present disclosure describedherein. Scope of the present disclosure is thus indicated by theappended claims, rather than by the foregoing description, and allchanges that come within the meaning and range of equivalency of theclaims are intended to be embraced therein.

What is claimed is:
 1. An integrated circuit (IC), comprising: asubstrate with a resistor region, the resistor region includes anisolation region in the substrate; a resistor body directly disposed onand contacts the isolation region; a plurality of first and secondcontacts/vias formed on the resistor body, wherein a resistor portion ofthe resistor body between the first and second contacts/vias forms aresistor; a terminal ILD layer disposed over the plurality of first andsecond contacts/vias; and first and second terminal plates which arenon-rectangular terminal plates disposed in the terminal ILD layer,wherein adjacent sides of the first and second terminal plates areseparated by a space and adjacent sides of the first and second terminalplates are slanted and configured to encompass the same number ofcontacts/vias.
 2. The IC of claim 1 comprising: first and secondalternating contact strips disposed on the resistor body along a firstdirection, wherein the first and second alternating contact strips serveas first and second resistor terminals; contact strip space regionswhich comprise silicide blocks separating the first and secondalternating contact strips; and a separate dielectric layer disposed onthe substrate, wherein the dielectric layer covers and contacts thesubstrate and the resistor body including the contact strips and contactstrip space regions.
 3. The IC of claim 2, wherein the contact stripscomprise metal silicide contact strips.
 4. The IC of claim 1, whereinthe resistor body comprises polysilicon, Ta, or TaN.
 5. The IC of claim4, wherein the resistor body comprises heavily doped polysilicon.
 6. TheIC of claim 1, wherein an outer perimeter of the first and secondterminal plates together has a size and shape similar to the resistorbody.
 7. The IC of claim 2, wherein the resistor body in the contactstrip space region separating the first and second alternating contactstrips forms a resistor.
 8. The IC of claim 1, wherein the terminalplates are trapezoidal shaped terminal plates and are slanted at anangle following the direction of current flow of the resistor.
 9. The ICof claim 2 comprising: a plurality of first conductive lines disposedabove a respective one of the first resistor terminals, the plurality offirst contacts/vias couple the respective one of the first resistorterminals to corresponding first conductive lines; and a plurality ofsecond conductive lines disposed above a respective one of the secondresistor terminals, the plurality of second contacts/vias couple therespective one of the second resistor terminals to corresponding secondconductive lines.
 10. The IC of claim 9, wherein: the first terminalplate is coupled to the first conductive lines; and the second terminalplate is coupled to the second conductive lines.
 11. The IC of claim 10,wherein: the first and second conductive lines are disposed on a firstmetal layer of the IC; and the first and second terminal plates aredisposed on a second metal layer of the IC.
 12. The IC of claim 11,wherein the first metal layer is a lowest metal layer (M₁) of the IC andthe second metal layer is a highest metal layer (Mx) of the IC, and x isan integer greater than
 1. 13. The IC of claim 12, wherein one or moreintermediate metal layers are disposed between M₁ and M_(x), the one ormore intermediate metal layers having a same pattern as that of theM_(x).
 14. The IC of claim 1, wherein the resistor is among a pluralityof on-chip resistors that are coupled in parallel.
 15. The IC of claim1, wherein the on-chip resistor is disposed below a bond pad of the IC.16. The IC of claim 10, wherein the non-rectangular terminal plateshaving adjacent sides which are slanted result in different firstconductive lines having different amount of contacts/vias and differentsecond conductive lines having different amounts of contacts/vias. 17.An integrated circuit (IC), comprising: a substrate with a resistorregion, the resistor region including an isolation region in thesubstrate; a resistor body directly disposed on and contacts theisolation region; a plurality of first contacts/vias coupled to theresistor body; a plurality of second contacts/vias coupled to theresistor body, wherein a resistor portion of the resistor body betweenthe first and second contacts/vias forms a resistor; a terminal ILDlayer disposed over the plurality of first and second contacts/vias; andfirst and second terminal plates which are non-rectangular shapedterminal plates disposed in the terminal ILD layer, wherein adjacentsides of the first and second terminal plates are separated by a spaceand adjacent sides of the first and second terminal plates are slantedand configured to encompass the same number of contacts/vias.
 18. The ICof claim 17, wherein the resistor body is a conductive metal comprisingTa, or TaN.
 19. The IC of claim 17, wherein the portion of resistor bodyforming the resistor is below a silicide block.
 20. The IC of claim 17,wherein an outer perimeter of the first and second terminal platestogether has a size and shape similar to the resistor body.
 21. The ICof claim 1, wherein the plurality of first and second resistor terminalscontacts the resistor body.
 22. The IC of claim 17 comprising: first andsecond alternating contact strips disposed on the resistor body along afirst direction; contact strip spaces separating the first and secondalternating contact strips; and wherein the first and second alternatingcontact strips serve as first and second terminals of the resistor. 23.The IC of claim 17, wherein the plurality for first and second resistorterminals contacts the resistor body.